The invention relates to a bone nail for the treatment of fractures in the proximal femur zone, comprising a distal end portion disposed at the outer surface of the femoral condyle, said end portion being provided with a coupling portion for engagement with a driving tool, a proximal end portion seated in the proximal femur and an arcuately curved portion between the ends.
Such a nail is known (West German Pat. No. 23 41 439; West German Utility Model No. 7 218 224). It is normally used together with several such nails (bunch nailing). The individual bone nails consisting of metal are provided with a diameter such that they are sufficiently elastic, so that they may be driven into the medullary canal of the femur via a window in the condyle of the femur. The proximal end of the nail seeks its way in the medullary canal and arrives in the femoral head via the femoral neck. The distal end of the nail is designed in such a manner that it is adapted to be brought into engagement with a drive-in tool. The bone nail is driven onward in the medullary canal with the aid of the drive-in tool while being watched on an image amplifier, with the first nail in particular having to be more or less rotated for repositioning the bone fragments. The powerful engagement of the drive-in tool at the distal end of the nail, thus, must be in a position also to transfer a substantial amount of torque onto the nail.
The known bone nails suffer from some disadvantages. The flattenings at the distal end which are oriented transversely to the axis of curvature and which are in addition provided with an aperture for the purpose of obtaining an effective engagement of a drive-in tool, may be effective in the manner of a chisel if they do not come to lie completely flat against the bone and in parallel therewith, respectively. The relatively sharp edges formed in this manner may have an irritating effect on the adjacent tissue. As the flattenings are normally formed in an upsetting process, additional processing is required so as to remove any burrs or sharp edges formed in said upsetting step. Through the flattening of a round nail cross sectional area, in addition, a critical zone of transition will form having a relatively high notch effect, so that with a considerable amount of torque applied at the distal end a plastic deformation or even a shearing off may be the result in this zone. Upon rotation of the distal ends against each other, several flattened distal ends require a relatively great amount of space, whereby the well-being of the patent may be affected.
So that the known nail bones may be driven onward more easily in the medullary canal it is known to taper them at the proximal end. Owing thereto, however, the danger exists that the proximal ends in the enck or in the head zone may protrude and enter the hip bone and the acetabulum, respectively, which is to be considered to be a serious complication of the method of treatment rendering it ineffective.